Material Cost Department of Mechanical Science and Engineering.ppt

,tam302engineeringdesignprinciples,syllabustopic:dfmafeaturebasedcosting,courseinstructor:mikephilpottdirectorofconcurrentdesign6/12-9.0/cu.in;+glass-16.3/cu.in):familywithoutstandingtoughnessandwearresistance.lowcoefficientoffriction.excellentchemicalresistanceandelectricalproperties.hygroscopic;dimensionalstabilityispoor.somegradesareelectroplatable.,commonthermoplasticmaterials(4),moldcosterbyiplas.htm,sheetmetalpartsprogressivedie,seespreadsheetonclasswebsiteformoredetails:sheetmetalmaterial.xls,step1materialcost,sheetmetal-progressivedies,progressivedieinoperation30ppm,progressivedieinoperation100ppm,step1materialcost(continued)progressivediemachinesarefedfromcoilstock.quiteabitofwastethathasnoreal$value.soassumelost.materialcost=blankweightxcost/kg/materialutilizationcoilwidthandpartpitch1.needtheser(smallestenclosingrectangleoftheflatpatternorunfoldedform.ifmodeledinproe,maybeabletogetthisautomatically.else,estimatebymeasurement.2.coilwidth=blankwidth+1/4”eachsideforcarrierstrip3.partpitch=blanklength+”forpilotholesblankweightblankvolume=coilwidth*partpitch*thicknesscost/kgdecideonmaterial,andlookupusingintablematerialutilizationassume100%utilizationhereasweareaccountingformostofthescrapthroughtheblankcomputation.1-2%wastefromendofcoilsmaysometimesbeincluded.,step2cycletimemucheasierthaninjectionmolding!cycletimeperpart=presscycletime/%uptimerulesformachineselection:1.theprogressivediesetmustfitonthepressbed:partwidth4:1),step4computehardtoolingcost(continued)hardtoolingcost=diebasecost+blankingcost+piercingcost+bendingcost+formingcost+drawcostamortizationvolume=annualproductionvolume*numberofpartsperproduct*productlifetoolingcostperpart=hardtoolingcost/amortizationvolumestep5totalcostperpartrecurringcosts:totalcostperpart=piecepartcost+toolingcostperpartnon-recurringcosts:investmentinmoldsanddies=hardtoolingcost,diecasting,costingdiecastparts,seefullspreadsheetonclasswebsite:diecastingmaterials.xls,step1materialcost,step1materialcost(continued)materialcost=partweightxcost/kg/materialutilizationweightdecideonmaterialcomposition,getvolumefromproe,densityfromdiecastingmaterials.xls,andcomputeweightcost/kglookupusingdiecastingmaterials.xlsmaterialutilizationassume95%utilizationfordiecasting.highbecausemostofrunnersandscrappartscanberemelted.,step2labortime(&cycletime)cycletimeisthetotaltimefromstarttofinishofthecastingcyclefordiecastingprocess:cycletime=dieclosetime+ladletime+injecttime+cooltime+dieopentime+partremovaltime+lubetime+trimtimerulesformachineselection(ref:diecastingmachine.xls)1.assumeasinglecavitymold2.smallestmachineismostcosteffective(lowestoverheadrate)3.themoldmustfitinthecastingmachine(tiebarlength/widthandmoldthickness)4.themachinemusthaveenoughforcecapability(seepressforcecalcsection)usingthedatefromprogressivediemachines.xlsanddiecastingmaterials.xls:dieclosetime:closeandlockdie(drycycletimespeconamachineisthetimetoopenandclosedieplates)dieclosetime=drycycletime/2ladletime:timetoladlemetalintoentrychamber.thisisonlyrelevantforcoldchamberprocess-hotchamber=1,coldchamber=2inmaterialtable)ladletime=(3+(volumeofpart/ladlerate)whereladlerate=125000mm3persec(typladlingspeedplus3sectoreplenishladlewithmetalfromreservoir),step2cycletime(continued)injecttime:injecttime=numberofcavities*0.035*partaveragethickness*(injecttemp-liquidustemp+61)/(injecttemp-moldtemp)youcanestimatetheaveragewallthicknesssimplyasthepredominantwallthicknesscoolingtime:cooltime=maxwallthickness*coolingfactor*(surfacearea/projectedarea)0.5)youcancalculatethemaxwallthicknesandprojectedareainthesamewayasyoudidforinjectionmolding.forsurfacearea,youcanuseproeanalysismodeorestimatemanually.dieopentime:closeandlockdie(drycycletimespeconamachineisthetimetoopenandclosedieplates)dieopentime=drycycletime/2partremovaltime:timetomanuallyremovethepartfromthediepartremovaltime=0.008*parthandlingsize+1(forparthandlingsize250)partremovaltime=3secs(otherwise)where:parthandlingsize=grippinglength+grippingwidthgrippingwidth=partwidth+125grippinglength=numberofcavities*partlength+125,step2cycletime(continued)dielubricationtime:spraydiesurfaceslubetime=0.0000511*lubearea+2.72lubearea=grippingwidth*grippinglengthtrimtime(assumeitisperformedbyoperatorwhilemachineiscycling)trimtime=0sofinallyaddalltogether:cycletime=dieclosetime+ladletime+injecttime+cooltime+dieopentime+partremovaltime+lubetime+trimtimetocomputepressforce:pressforce=projectedareaofpart*numberofcavities*safetymargin*clampingpressure(fromdiecastingmaterials.xls)assumesafetymargin=1.5(i.e.50%safetyfactor),step3computepiecepartcostthecycletimedrivesthesetwoimportantcostelementscycletimeperpart=cycletime/numberofcavitieslabortimeperpart=cycletime*laborrationlaborcost=labortimeperpart*laborrate($/hr)directoverheadcost=cycletimeperpart*overheadrate($/hr)setupcost=setuptime*(laborrate+overheadrate)/(annualvolume*numberofpartsperproduct/numberofbatchesperyear)so:piecepartcost=materialcost+laborcost+overheadcost+setupcost,step4computehardtoolingcosthardtoolingcost=useiplastoolingcostestimatoronclasswebsitethisisforinjectionmoldtoolingbutverysimilarconceptandabout10%moreexpensivesomultiplyresultby1.1,amortiz